1. Field of the Invention
The present invention relates generally to manufacturing of record discs, and more particularly is directed to a method of manufacturing a record matrix from a lacquer master.
2. Description of the Prior Art
In the art of producing phonograph record discs, at first, a lacquer master having a sound groove is prepared, a record matrix having a projection strip corresponding to, or coincident with the sound groove of the lacquer master is prepared from the lacquer master and a record disc is molded by the record matrix. When a large number of record discs are to be molded, a mother is provided from the record matrix which is a first record matrix, then one or more metal stampers or second matrices each having the above projection strip are prepared from the mother, and a number of record discs are manufactured from each stamper. In a known method for manufacturing the record matrix from the lacquer master, a surface metal layer of nickel is formed, by electro-less plating, on the surface of the lacquer master having the sound groove therein so that the surface metal layer is formed with a projecting strip corresponding to the sound groove; whereupon, the reinforcing layer, for example, of nickel, is electro-plated over the surface metal layer and, thereafter, the reinforcing layer together with the surface metal layer are peeled or separated from the lacquer master to form the record matrix.
In a known method for the electro-less plating of nickel, for example, for forming the surface metal layer on the lacquer master in the above described procedure for producing a record matrix, the surface to be plated is first degreased by rinsing with a neutral washing agent and then washed with water prior to being subjected to a so-called anchoring treatment by immersion in a chromic acid mixture for 30 seconds. Following such anchoring treatment which forms fine concave and convex portions on the surface to be plated, the lacquer master is again washed with water and then immersed for three minutes in a stannous chloride bath and in a palladium chloride bath for increasing the sensitivity and activity of the surface to be plated. Thereafter, a metal salt solution containing approximately 0.19 mol/l of nickel sulfate and 0.95 mol/l of ammonium chloride and a reduction solution containing 0.05 mol/l of sodium borohydride are sprayed together with inert and reducing gases against the surface to be plated.
By reason of the so-called anchoring treatment included in the above disclosed electro-less plating method, the plated nickel layer that results from the sprayed metal salt and reduction solutions will mesh with the above mentioned fine concave and convex portions and hence the adhesion of the plated layer to the lacquer master surface is strengthened. The above anchoring treatment, however, requires much work and, when electric power is applied to the electro-less plated layer, for example, when effecting further nickel electro-plating on the electro-less plated layer to provide a reinforcing layer, some peeling-off portions or scabs are formed in the plated layer. In other words, in the above prior art method, the anchoring treatment is required to ensure adequate deposit of the electro-less plated nickel layer on the surface of the lacquer master but the resulting electro-less-plated layer has surface irregularities corresponding to the fine concave and convex portions formed by the anchoring treatment and, as a result thereof, in the course of a subsequent electro-plating of nickel on the electro-less-plated layer, scabs, projections, cracks or peeling-off portions are generated and these are fatal defects in manufacturing a record matrix. Moreover, the chromic acid mixture used for the anchoring treatment is a noxious source of pollution which it is difficult to control.